Variable capacitive voltage divider



Oct. 17, 1939.

W. BERNDT VARIABLE CAPACI'IIVE VOLTAGE DIVIDER Filed 001;. 20, 1937 INV EN TOR Y 214 LTER BERNDT B W ATTORNEY.

Patented Oct. 17, 1939 VARIABLE CAPACITIVE VOLTAGE DIV IDER- Walter Berndt, Berlin, Germany, assignor to Telefunken Gesellschaft fiir Drahtlose Telegraphic in. b. H., Berlin, Germany, a corporation of Germany Application October 20, 1937, Serial No. 169,965 In Germany October 20, 1936 9 Claims. (Cl. 178-44) This invention is concerned with a variable being closed at the ends. Located inside the same capacitive voltage divider, especially adapted to is another, similar cylinder B arranged so as to be field-intensity measuring means and measuring capable of rotation. Supported inside of cylintransmitters. der A is the insulated fixed plate P1, while cyl- For radio frequency voltage division the followinder B is provided with the outside plate P2. ing arrangement has been used in the prior art to Both cylinders are metallically connected with act as a capacitive potentiometer possessing a each other. Rotation of B is feasible from the large range of regulation: At one end inside a outside by the intermediary of a suitable spindle cylindrical tube is mounted a fixed insulated or shaft on which may be provided a convenient plate, while placed opposite thereto is a second fi e-adjus ment Ca b at o (Ve e as k ow 10 plate being shiftable in axial direction. If the in the art. In lieu of the plates P1 and P2, there input potential between the fixed plate or coat could be used also cyl plate assemblies and the tube is constant, the output potential the like. between the movable coat and the tube will vary If the input potential is impressed across 1 roughly in logarithmic proportion to the distance and A, then the diminished or divided potential between the two coats o-r plates. And the range ay be ta n f across 2 a d A. The same (1 of adjustment will be so much larger, the greater minishes pp o y W the angle of ro the length of the tube compared to its diameter. tion according to a lo c f the n e In lieu of the plates or coats, also cylinders and of rotation is over 180,the same would rise a mushroom-shaped arrangements have been em- In order that this may be avoided, a radial shieldployed. mg wall or partition S is built in upon one side However, po-tentiometers of this known kind of P1 which is in conducting relationship with involve drawbacks, several of which are menthe inner and outer cylinders. In this instance, tioned below. The mounting thereof in a set is he angl of dj tm o setting am n to attended with difficulties because of the comparaea y 36 tively great length. Adjustment by longitudinal A constant input Capacity of the potentiometer shift is not convenient and is inexact. The cais insured by Connecting p y in parallel pacity between the fixed or stator plate and the to the input, said capacity decreasing with apouter shell is not independent of the position of proach of P2 and P1 in the same measure as the mobile plate. In fact, it grows as the movable the capac ty 2 Capacity w The plate approaches the stator plate, and this so said compensating capacity may be driven by much more so the higher the capacitive load of any suitable agency. the output. This fact makes itself felt in a par- An exemplified embodiment of the latter scheme ticularly annoying way whenever the input end is shown in Fig. 2. Opposite the plate assemis associated with a resonance circuit, for the bly P2 is a compensator plate K, the distance natural wave is then found to be subject to of which grows in the neighborhood of P1. By constant changes as the potentiometer is set. ways and means known in the art the distance Now, these various shortcomings are obviated between K and P2 may be set and fixed at any in an arrangement as hereinafter disclosed. Acdesired point or Value from the outside. The cording to the invention the-re are mounted in result is that the capacity between P2 and the the space between two metallic cylinders which cylinder is practically independent of the angle are rotatable inside each other concentrically, two of rotation.

capacity plates or plate systems or assemblies, one The range of regulation of the potentiometer of which is secured to the outer and the other one is so much larger, the greater the mean length to the inner cylinder so as to be insulated thereof rotation of the movable plate compared with from. The voltage to be divided is impressed the cross-section in which the plate moves.

between the cylinder arrangement and one of What is claimed:

the p While the divided potential is taken 1. Variable capacitive voltage divider, with the off across th Cy arrangement d the other characteristic feature that in the space between p two concentrically and rotatably arranged and 5 T e following is a more detailed description electricallyinterconnected metallic cylinders, two

of the i ve eooempevhied by a drawing Where capacity plate systems are disposed, one of whichis in Figs. 1 and 2 illustrate two embodiments of the secured on th outer and th other one t t invention. I inner cylinder in an insulated manner, and that R e g to Fig, A is a metallic Cylinder the voltage to be divided is impressed between the cylinder arrangement and one of the plate systems, while the subdivided potential is taken oif across the cylinder arrangement and the respective other plate system.

2. Variable capacitive voltage divider as claimed in claim 1, with the characteristic feature that upon one side of one of the capacity plate systems is arranged a radial metallic screening wall which is connected with the cylinders.

3. Variable capacitive voltage divider as claimed in claim 1, with the characteristic feature that the cylinder arrangement is shut at its ends.

4. Variable cylindrical voltage divider as claimed in claim 1, with the characteristic features that the plate systems consist of a plurality of elementary plates adapted to interleave combfashion.

5. Variable capacitive voltage divider as claimed in claim 1, with the characteristic feature that with a view to stabilizing the input capacity, a capacity varying with the angle of rotation of the voltage divider is connected in parallel relation to the input.

6. A variable capacitive voltage divider comprising concentric inner and outer metallic tubes, said inner tube being rotatable, a fixed metallic plate disposed in the space between said tubes and insulatingly secured to said outer tube, and another metallic plate also disposed in the space between said tubes, said last plate being insulatingly secured to said inner tube and rotatable therewith, an input circuit coupled between the outer tube and one plate, and an output circuit coupled between the inner tube and said other plate.

7. A variable capacitive voltage divider comprising concentric inner and outer metallic tubes metallically connected together, said inner tube being rotatable, a fixed metallic plate disposed in the space between said tubes and insulatingly secured to said outer tube, and another metallic plate also disposed in the space between said tubes, said last plate being insulatingly secured to said inner tube and rotatable therewith, an input circuit coupled between one of said tubes and one plate, and an output circuit coupled between said same tube and said other plate.

8. A variable capacitive voltage divider comprising concentric inner and outer electrically connected cylindrical tubes, one of which is rotatable, a pair of capacity plates in the space between said tubes, said plates being insulated from each other and from said tubes, one of said plates being fixedly positioned while the other of said plates is insulatingly secured to the rotatable tube and movable therewith, said voltage divider being adapted to have the voltage impressed between one of said tubes and one of said plates while the subdivided voltage is derived from between said tube and the other plate.

9. A variable capacitive voltage divider comprising concentric inner and outer electrically connected cylindrical tubes, one of which is rotatable, a pair of capacity plates in the space between said tubes, said plates being insulated from each other and from said tubes, one of said plates being fixedly positioned while the other of said plates is insulatingly secured to the rotatable tube and movable therewith, an input circuit coupled between one of said plates and one of said tubes, an output circuit coupled between said other plate and said tube, and means including a capacitor arranged in parallel relation to said input circuit for maintaining the capacity thereof substantially constant with rotation of the rotatable tube.

WALTER BERNDT. 

